is that like the only tutorial on adding BtS leaderheads? because i already tried that one
I have had problems adding leaderheads too. I find it's easier just to change them. What I do is pick a leaderhead I won't want to use in the scenario, if possible one that is related to the civ I want to add, and use that as a base. For example, say I want to create a Scottish civ with leader Macbeth. I would base it on Brennus. Then I would download the leaderhead art I want to use and just change Brennus's info in Civ4ArtDefines_Leaderhead.xml. That's really all you
need to do, though of course that only changes the look. Everything else about him is still Brennus.
So next I would change his Civilopedia entry, his textinfo, etc. Because basically, in Civ, the text inside a tag is (usually) just a reference to something else (except in the Text directory). For example, the text under <Tag>TXT_KEY_LEADER_BRENNUS_PEDIA</Tag> in CIV4GameText_Civilopedia_CivLeaders.xml does not have to be about Brennus. It can be anything. You can just replace the Brennus entry with the Wikipedia entry for Macbeth.
Be sure to do a search for LEADER_BRENNUS in all the XML files in C:\Program Files\Firaxis Games\Sid Meier's Civilization 4\Assets\XML\ and possibly also in the Warlords and BTS directories, depending on the leaderhead you are using as your base. Make sure you have all those files in your mod and that you change them so they fit your new leaderhead.
After you do all of that you essentially have a new leaderhead, though you lost an old one. If you really want to get the old one back, you can change "LEADER_BRENNUS" to "LEADER_MACBETH" in all your mod files and then go back and add the old Brennus by copying and pasting the Brennus entries from the original game files.
The nice thing about this method is you don't break anything, so the game won't blow up when you select an incorrectly configured leaderhead.
I've also sometimes had issues with the <NoShaderNIF> tag. Some leaderheads don't have one, in which case you can just make the tag empty by replacing it with <NoShaderNIF/>. Sometimes the <NoShaderNIF> is the same as the <NIF>, so just use the same text inside both tags.